An electronic discharge lamp ballast has been accepted as having an inherent capability of providing a relatively high re-ignition voltage to a discharge lamp reaching its near end of lamp life for prolonging the lamp life. However, this advantage may sometimes cause the lamp to suffer from undue stress which would deteriorate an arc tube of the discharge lamp. The typical deterioration is a leakage of a filling gas out of the arc tube. Once the leakage becomes critical, an abnormal arc discharge would occur within an envelop surrounding the arc tube when supplying the AC output power to the arc tube. That is, the abnormal arc discharge would develop between an electrode of the arc tube and a certain conductive part within the envelope. If such abnormal arc discharge continues, the discharge lamp would be damaged.
Also, if there be any discontinuity in the electric feeding line from the ballast to the discharge lamp due to the disconnection or a dielectric breakage in a covering of the feeding line, like abnormal arc discharge would develop in the feeding line, thereby damaging the ballast, the connection, and/or the discharge lamp itself.